No optimal way. Sad indeed.
I can export the edited Aperture RAW as a TIFF, but it’s enormous at 75Megs.
I think my confusion is that I have hundreds of RAW photos that were successfully imported into Photos (And the M key works). Those RAWs were done when I imported my entire Aperture library into Photos. So the fact is that there is no way to replicate that process.
I'm tempted to delete my entire Photos Library and reimport my up to date Aperture library and then figure out some other way to keep them synced. Would that be a safe thing to do?
Like many others I live with the vanishing hope that Photos will eventually be a contender and so I'm foolishly putting off the day when I'm forced to move on. I'm not happy with most of the alternatives I've tried.